Cooling

An engine climbing too high in temperature is one of those situations where reacting fast really makes the difference: excessive heat is the direct enemy of internal parts, and a few minutes too many can turn a minor incident into a heavy repair. Understanding how your motorcycle sheds its heat is therefore the mark of a good owner.

Not all motorcycles cool the same way, and that's the first thing to know. Liquid-cooled models have a full circuit — radiator, pump, thermostat, fan, hoses — each element of which can fail. Air-cooled (or air-oil) models have no such circuit: for them, overheating comes down to oil level, the cleanliness of the fins, mixture richness, or long stops in traffic.

The warning signs overlap: temperature rising abnormally, a fan running constantly, a sweetish smell, fluid lost on the ground or in the expansion tank. On an air-cooled bike, a coolant leak simply can't happen — a useful marker so you don't look in the wrong place.

A few simple checks spare you a lot of trouble, especially in warm weather when overheating multiplies in traffic. On a liquid-cooled bike, check the level in the expansion tank with the engine cold, the condition of the hoses, and the cleanliness of the radiator's front face, often clogged with insects and dust. On an air-cooled bike, the oil level and the cleanliness of the fins play the radiator's role: never neglect them. And if the fan doesn't kick in when the temperature rises at a standstill, that's a priority trail to explore.

Two normal behaviours are often mistaken for faults, and knowing them saves needless worry. First, on a liquid-cooled bike it's normal for the fan to kick in at a standstill when the temperature rises, then cut out: that's its job. Second, after a top-up or a coolant change, trapped air can cause a false overheat or uneven warming until it's bled out. Conversely, a fan that never starts, a temperature that climbs while riding (when airflow should be cooling the engine), or an overflowing tank are real signals. Telling the two apart is already half the diagnosis.

Choose the symptom that matches your situation to start the diagnosis. And if the engine overheats while riding, the right move is simple: shut it down as soon as you can, let it cool, and never open a still-hot circuit cap — pressurised coolant can scald badly. When in doubt, have it checked rather than pressing on: better to spend 30 € on a diagnosis than 300 € on damage.